Conventional radio frequency power amplifiers that typically use field effect transistors have an optimal gate to source voltage operating point where the output power and gain are at the maximum. This operating point is related to input drive signal frequency. However, such conventional radio frequency power amplifiers have a pre-set substantially constant gate to source voltage and therefore it is not possible to maintain maximum, or near maximum, gain and output power over a wide range of input signal frequencies. In addition, conventional radio frequency power amplifiers have an associated pre-set voltage bias circuitry, typically comprising a Digital to Analogue converter when the amplifier is part of a microprocessor controlled radio. This bias circuitry is relatively expensive and the bias has to individually set for each manufactured amplifier, this can be time consuming and the bias is susceptible to drift.